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From: Yeb Havinga on 13 Jul 2010 04:50
Tom Lane wrote:
> The reason I'm on about this at the moment is that I think I see how to
> get ruleutils to print PARAM_EXEC Params as the referenced expression
> rather than $N ...
Wouldn't this obfuscate the plan more than printing subplan arguments at
the call site?

regards,
Yeb Havinga


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From: Tom Lane on 13 Jul 2010 10:10
Yeb Havinga <yebhavinga(a)gmail.com> writes:
> Tom Lane wrote:
>> The reason I'm on about this at the moment is that I think I see how to
>> get ruleutils to print PARAM_EXEC Params as the referenced expression
>> rather than $N ...

> Wouldn't this obfuscate the plan more than printing subplan arguments at
> the call site?

It would if subplans could have more than one call site, but they can't.

I do intend to force qualification of Vars that are printed as a result
of param expansion; for example consider a standard nestloop-with-
inner-indexscan plan:

NestLoop
Seq Scan on a
Index Scan on b
Index Cond: x = a.y

If y weren't qualified to show that it's not a variable of b, this could
be confusing. But as long as we do that, it pretty much matches our
historical behavior. Note that CVS HEAD is printing this case as

NestLoop
Seq Scan on a
Index Scan on b
Index Cond: x = $0

which is definitely not very helpful.

regards, tom lane

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From: Yeb Havinga on 13 Jul 2010 11:21
Tom Lane wrote:
> Yeb Havinga <yebhavinga(a)gmail.com> writes:
>
>> Tom Lane wrote:
>>
>>> The reason I'm on about this at the moment is that I think I see how to
>>> get ruleutils to print PARAM_EXEC Params as the referenced expression
>>> rather than $N ...
>>>
>> Wouldn't this obfuscate the plan more than printing subplan arguments at
>> the call site?
>>
>
> It would if subplans could have more than one call site, but they can't.
>
> I do intend to force qualification of Vars that are printed as a result
> of param expansion;
>
Will the new referenced expression printing also be used when printing
subplans?

If yes, I do not have to submit the latest version of a patch I made for
subplan argument printing (discussed earlier in this thread
http://archives.postgresql.org/pgsql-hackers/2010-02/msg01602.php)

regards,
Yeb Havinga


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From: Tom Lane on 13 Jul 2010 14:14
Yeb Havinga <yebhavinga(a)gmail.com> writes:
> Will the new referenced expression printing also be used when printing
> subplans?

> If yes, I do not have to submit the latest version of a patch I made for
> subplan argument printing (discussed earlier in this thread
> http://archives.postgresql.org/pgsql-hackers/2010-02/msg01602.php)

Oh, I had forgotten that patch was still in progress. I think it's
unnecessary given what I'm fooling with. The attached patch needs
some more testing, but what I get with it is for example

regression=# explain (verbose) select (select oid from pg_class a where
regression(# a.oid = b.relfilenode) from pg_class b;
QUERY PLAN
--------------------------------------------------------------------------------------------------------
Seq Scan on pg_catalog.pg_class b (cost=0.00..5556.81 rows=669 width=4)
Output: (SubPlan 1)
SubPlan 1
-> Index Scan using pg_class_oid_index on pg_catalog.pg_class a (cost=0.00..8.27 rows=1 width=4)
Output: a.oid
Index Cond: (a.oid = b.relfilenode)
(6 rows)

(this is the first example in the above-referenced thread).

regards, tom lane

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